1. Weathering and Erosion
Essential Question: How does weathering and erosion shape our Earth?

2. What is Weathering? Weathering is the process of breaking down rocks
Two forms of weathering:
Mechanical/Physical
Chemical

3. What is Mechanical Weathering?
Mechanical weathering is breaking down by natural or physical processes

4. The 3 Types of Mechanical Weathering

5. 1. ICE WEDGING
When water goes into fractures in rock and freezes, the force of expansion is great enough to break the rock into smaller pieces.

6. Mount Rushmore – South Dakota
Bryce Canyon – Utah

7. 2 . Abrasion Abrasion Collision of rocks Makes rocks more spherical
Bighorn Mountains – Wyoming
Antelope Canyon – Arizona
Wyoming
What causes abrasion?
1. Water
2. Wind
Elephant Rocks Park – Missouri
3. Ice
4 . Gravity

8. Not Just Limited to Rocks…..

9. 3. Root Action
Slow process
When roots spread to break rock

11. Close to Home

12. What is Chemical Weathering?
Chemical weathering occurs when minerals are chemically changed causing them to dissolve or change to another mineral
Oxidation
Acid
Plants

13. Oxidation
Oxidation - chemical reaction with oxygen and iron rich rocks. Causes rocks to “rust”
iron-rich rock have reddish stains from "rusting" due to iron and oxygen reacting

15. Close to Home

16. Plant Acids
Some roots and decaying plants give off acids that also dissolve minerals in rock. When these minerals dissolve, the rock is weakened.
Eventually, the rock will break into smaller pieces.

17. Plants
Plants – called lichens produce rock dissolving acids that can break down rock.

18. Acid precipitation (Acid Rain)
Sulfur & CO2 from cars and coal/oil mix with water to produce acidic precipitation.
Rain
Snow
Sleet
Hail

19. How does the Environment affect Weathering?
Temperature
Different temps give different type of weathering
Moisture
High moisture, chemical
Weathering
Low moisture, mechanical

20. Effects of Climate
Chemical weathering is more rapid in warm, wet climates.
Lack of moisture in deserts and low temperatures in polar regions slow down chemical weathering.
In cold climates, where freezing and thawing are frequent, mechanical weathering rapidly breaks down rock through the process of ice wedging.

21. IDENTIFY THE PROCESS!!!

22. 1

23. 1-Abrasion Mechanical

24. 2

25. 2-Onion Skin Weathering Mechanical

26. 3

27. 3-Chemical Water is wearing away the rock

28. 4

29. 4-Freezing and Thawing Mechanical

30. 5

31. 5-Mechanical

32. 6

33. 6-Mechanical & Chemical….how?

34. 7

35. 7-Mechanical Animal Actions

36. 8

37. 8-Mechanical with a little Chemical

38. 9

39. 9-Chemical

40. 10

41. 10- Mechanical but could possibly be chemical

42. 11

43. 11-Another rusted bike!

44. 12

45. 12-Release of Pressure Mechanical

46. 13

47. 13-Chemical – Lichen grow, they release chemicals when they grow

48. 14

49. 14-They call this Potato Chip Rock Could mechanical or chemical….

50. 15

51. 15-Freezing and Thawing Mechanical

52. 16

53. 16-Chemical-Water

54. 17

55. 17-See the different colors in the rock Chemical from oxidation

56. 18

57. 18-Mechanical What role do humans play in weathering of Earth’s surface?

58. What is Erosion?
Erosion is the removal and transport of material from one place to another

59. What are the agents of Erosion?
There are 4 main agents of erosion:
Gravity
Water
Glaciers
Wind

60. What happens to the sediments?
When sediments are eroded (moved), they are not lost from Earth—they are just relocated
Deposition is when sediments are moved and deposited or “dropped off”
Weathering, erosion, and deposition act
together in a cycle that wears down and
builds up Earth’s surface

61. How does Gravity cause Erosion?
A mass movement is any type of erosion that happens as gravity moves materials down slope
Landslides
Mudslides
Rock slides

62. What are the different types of mass movement?
Landslide is the most destructive kind of mass movement. It is when rock and soil slide quickly down a steep slope
Mudflow is a rapid downhill movement of a mixture of water, rock, and soil. Usually occurs after heavy rains in normally dry areas.

63. What are the different types of mass movement?
Slump is a mass of rock and soil suddenly slips down a slope. The difference is that the material in a slump moves in one large mass.
Creep is very slow downhill movement of rock and soil. Often a result of freezing and thawing of water in cracked layers of rock beneath the soil. It is so slow, you can hardly notice it!

64. Self Check What is erosion?
What type of mass movement is shown in this illustration?
What are the 4 agents of erosion?

65. How do Glaciers cause Erosion?
A glacier is a large mass of ice and snow moving on land under its own weight
As glaciers pass over land, they erode it, changing features on the surface
Glaciers then carry eroded material along and deposit it somewhere else.
There are 2 types of glaciers: Continental (covers most of a continent) and Valley Glaciers (in the valley between 2 mountains)

67. How do Glaciers shape the land?
The movement of a glacier changes the land beneath it
Although glaciers work slowly, they are a major force of erosion
The two process by which glaciers erode the land are plucking and abrasion 67

68. How do Glaciers shape the land?
As a glacier flows over the land, it picks up rocks in a process called plucking
Due to the glaciers extreme weight, it can break rocks apart and then the rocks freeze to the bottom of the rock carrying it with it when it moves
As rocks remain on the bottom of the glacier and it drags them across the land, abrasion occurs as it scratches the bedrock
When a glacier melts, it deposits the sediment it eroded from the land creating various landforms 68

69. How does wind contribute to erosion?
Wind by itself is the weakest agent of erosion, however, it can be a powerful force in shaping the land areas where there are few plants to hold the soil in place
Sand dunes are mounds of sediment drifted by the wind
Dunes can be see along shore of oceans, but are common in desert regions

70. Self Check What are two ways in which glaciers erode Earth’s surface?
What is the difference between a continental and a valley glacier?

71. How is water an agent of Erosion?
Moving water is the major agent of erosion that has shaped Earth’s land surface
Through erosion, a river creates valleys, water falls, flood plains, and other landforms
Deposition of sediments creates landforms such as deltas and also adds soil to a river’s flood plain
A delta is sediment that are deposited where a river flows into an ocean or lake building up a landform 71

72. How is water an agent of Erosion?
Ground water is another agent of erosion through the process of chemical weathering
Ground water is water that fills the cracks and spaces in underground soil and rock layers
Ground water containing carbonic acid can break down limestone creating caves or caverns.
Stalactites and stalagmites are also formed from the deposit of calcite due to chemical weathering 72

73. How do waves contribute to Erosion?
The energy in waves comes from wind that blows across the water’s surface
Waves shape the coast through erosion by breaking down rock and transporting sand and other sediment
Waves shape a coast when they deposit sediment, forming coastal features such as beaches, sand bars, and sea arches 73

74. Self Check What is the source of the energy in ocean waves?
What process is the cause of ground water erosion (mechanical or chemical)?